Civil & Structural Engineers on WTC Collapse

This is a blog dedicated to all the engineers that have spoken out about what happend on 9/11 but were quotemined by the "truthmovement". I have also added Engineers that just commented on the events that day.
I will be updating this blog reguraliry.

I guess a lot of you have heard about the website ae911truth where a group of individuals claim that what happened to WTC 1, 2 and 7 could not have happened. This is just a claim, because they have nothing to show for their allegation that it could not have happened the way it did. You won't find any calculations that show how the NIST Report is wrong. On this site, you will find many structural engineers - those who actually know what they are talking about - explaining why the towers collapsed the way they did. So feel free to look at all the information I have gathered about the research done on the collapse on the towers. The research has been published in numerous engineering magazines and all over the internet on engineering sites (See the links on the right side of this site).

Only a handful of architects and engineers question the NIST Report, but they have never come up with an alternative. Although at first blush it may seem impressive that these people don't believe the NIST Report, remember that there are 123,000 members of ASCE(American Society of Civil Engineers) who do not question the NIST Report. There are also 80,000 members of AIA(American Institute of Architects) who do not question the NIST Report.

Although their field of expertise is not related to the construction of buildings - they don't seem to have a problem with that over at AE911truth - there are also 120,000 members of ASME(American Society of Mechanical Engineers) who do not question the NIST report. There are also 370,000 members of IEEE(Institute of Electrical and Electronics Engineers) who do not question the NIST report. There are also 40,000 members of AIChE(American Institute of Chemical Engineers) who do not question the NIST Report. There are also 35,000 members of AIAA (American Institute of Aeronautics and Astronautics) who do not question the NIST report. So who would you rather believe?

Although most Americans believe they know what brought down the World Trade Center twin towers on Sept. 11, 2001, civil engineers are still seeking answers to questions that could save lives in the future.

Structural engineers need to know from a scientific perspective what happened to the buildings during the terrorist attacks in order to prevent future failures. The search for answers continues with the help of a state-of-the-art animated visualization created by researchers at Purdue University.

Christoph Hoffmann, a professor of computer science and director of Purdue's Rosen Center for Advanced Computing, a division of Information Technology at Purdue, says the animation reveals more information than could be conveyed through a scientific simulation alone.

that are absolutely essential to the engineer," Hoffmann says. "This gives us a simulation that doesn't deliver much visual information to a layperson. Our animation takes that scientific model and adds back the visual information required to make it a more effective communication tool."

The scientific simulation, the completion of which was announced last September, required several test runs before the researchers were satisfied; the final test run required more than 80 hours of high-performance computing. The simulation depicts how a plane tore through several stories of the World Trade Center north tower within a half-second and found that the weight of the fuel acted like a flash flood of flaming liquid, knocking out essential structural columns within the building and removing fireproofing insulation from other support structures. The simulation used lines and dots to show the aircraft and building during the event.

To develop the new animated visualization, Voicu Popescu, an assistant professor of computer science, developed a translator application that creates a link between computer simulations and computer visualization systems to automatically translate simulation data into a 3-D animation scene.

"This translator is scalable and can be used in other simulations," Popescu says.

In the animation, elements that were not part of the scientific simulation, such as flames and smoke, are clearly rendered, although the visualization does not show the subsequent effects of the fire.

Even though details were added in this animation, Popescu says the visualization was intentionally kept "non-descript" so that they would not be exploitive of the horrific attack.

"For example, on the airplane there are no airline insignia or windows," Popescu says.

Still, Popescu says the visualization has a realism never seen before.

"The crashes and computer models you often see on television are not scientifically accurate," he says. "This provides an alternative that is useful to the nonexpert but is also scientifically accurate, so it provides a more realistic picture of the event."

The visualization begins with a Google Earth map of lower Manhattan as it appeared on Sept. 11, 2001. The video then shows the damage caused by the aircraft as it hit the north tower, follows the disintegrating plane through the interior, and then shows the airplane metal, ignited fuel, dust and smoke exiting the building on the opposite side.

The simulation found that the airplane's metal skin peeled away shortly after impact and shows how the titanium jet engine shafts flew through the building like bullets.

As with an earlier simulation developed by this team that examined the 9/11 attack on the Pentagon, the World Trade Center simulation showed that it was the weight of the 10,000 gallons of fuel more than anything else that caused the damage.

"It is the weight, the kinetic energy of the fuel that causes much of the damage in these events," Hoffmann says. "If it weren't for the subsequent fire, the structural damage might be almost the same if the planes had been filled with water instead of fuel."

Mete Sozen, Purdue's Kettlehut Distinguished Professor of Structural Engineering and a principal investigator on the simulation project, says the researchers worked for years and used the best computing resources available to recreate the event.

"To estimate the serious damage to the World Trade Center core columns, we assembled a detailed numerical model of the impacting aircraft as well as a detailed numerical model of the top 20 stories of the building," Sozen says. "We then used weeks of supercomputer time over a number of years to simulate the event in many credible angles of impact of the aircraft."

Sozen says the actual damage to the building's facade that was observed was identical to the damage shown by the numerical simulation.

"We calibrated our calculations using data from experiments we had conducted to evaluate the energy imparted from fluid moving at high speed to solid targets," he says. "We concluded that the damage map we calculated for our numerical model of the building would correspond closely to the actual extent of the damage."

The simulation represented the plane and its mass as a mesh of hundreds of thousands of "finite elements," or small squares containing specific physical characteristics. In the visualization, these scientific data points are used to show how airplane components swept through the building and out through the other side as the fuel ignited.

"The aircraft moved through the building as if it were a hot and fast lava flow," Sozen says. "Consequently, much of the fireproofing insulation was ripped off the structure. Even if all of the columns and girders had survived the impact - an unlikely event - the structure would fail as the result of a buckling of the columns. The heat from an ordinary office fire would suffice to soften and weaken the unprotected steel. Evaluation of the effects of the fire on the core column structure, with the insulation removed by the impact, showed that collapse would follow whatever the number of columns cut at the time of the impact."

The animation is the latest in a series of projects by the Purdue team that arose after 9/11 to determine the structural damage that occurs when an airplane collides with a building. Although one goal was to develop structures that can withstand a terrorist attack, the team also has used this research to investigate other scenarios, such as an airplane inadvertently crashing into a building located near an airport.

"This is important work that has many more applications than we first thought," Hoffmann says. "The important thing is that we are learning so much in so many different areas."

Note to Journalists: Broadcast-quality DVDs of the animation without the researcher's narration are available in both standard quality and high definition from Steve Tally, (765) 494-9809, tally@purdue.edu

IMAGE CAPTION 1:Purdue researchers have developed a scientifically based video animation of the 9/11 attacks on the World Trade Center. Their research has found that it was the weight of the fuel combined with the fire, and not the aircraft itself, that caused the most damage to the buildings. This information can be used by engineers to build new structures that are better able to withstand such attacks, the researchers say. (Purdue University image/Voicu Popescu)

IMAGE CAPTION 2:A scientifically based video animation of the 9/11 attacks on the World Trade Center by researchers at Purdue shows that it was the weight of the fuel combined with the fire, and not the aircraft itself, that caused the most damage to the buildings. Only a few parts of the airplane, such as the titanium jet propeller shafts, actually continued through the building, the researchers say. (Purdue University image/Voicu Popescu)

Recommendation 1. NIST recommends that: (1) progressive collapse be prevented in buildings through the development and nationwide adoption of consensus standards and code provisions, along with the tools and guidelines needed for their use in practice; and (2) a standard methodology be developed—supported by analytical design tools and practical design.

Affected Standards: ASCE-7, AISC Specifications, and ACI 318. These standards and other relevant committees should draw on expertise from ASCE/SFPE 29 for issues concerning progressive collapse under fire conditions. Model Building Codes: The consensus standards should be adopted in model building codes (i.e., the International Building Code and NFPA 5000) by mandatory reference to, or incorporation of, the latest edition of the standard. State and local jurisdictions should adopt and enforce the improved model building codes and national standards based on all 30 WTC recommendations. The codes and standards may vary from the WTC recommendations, but satisfy their intent.

Recommendation 2. NIST recommends that nationally accepted performance standards be developed for: (1) conducting wind tunnel testing of prototype structures based on sound technical methods that result in repeatable and reproducible results among testing laboratories; and (2) estimating wind loads and their effects on tall buildings for use in design, based on wind tunnel testing data and directional wind speed data.

Affected National Standard: ASCE-7. Model Building Codes: The standard should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 3. NIST recommends that an appropriate criterion be developed and implemented to enhance the performance of tall buildings by limiting how much they sway under lateral load design conditions (e.g., winds and earthquakes).

Affected National Standards:ASCE-7, AISC Specifications, and ACI 318. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

the effect of spaces containing unusually large fuel concentrations for the expected occupancy of the building; and

the extent to which fire control systems, including suppression by automatic or manual means, should be credited as part of the prevention of fire spread.

Model Building Codes: A comprehensive review of current construction classification and fire rating requirements and the establishment of a uniform set of revised thresholds with a firm technical basis that considers the factors identified above should be undertaken.

Recommendation 5. NIST recommends that the technical basis for the century-old standard for fire resistance testing of components, assemblies, and systems be improved through a national effort. Necessary guidance also should be developed for extrapolating the results of tested assemblies to prototypical building systems. A key step in fulfilling this recommendation is to establish a capability for studying and testing the components, assemblies, and systems under realistic fire and load conditions.

Affected National and International Standards: ASTM E 119, NFPA 251, UL 263, and ISO 834. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 6. NIST recommends the development of criteria, test methods, and standards: (1) for the in-service performance of sprayed fire-resistive materials (SFRM, also commonly referred to as fireproofing or insulation) used to protect structural components; and (2) to ensure that these materials, as-installed, conform to conditions in tests used to establish the fire resistance rating of components, assemblies, and systems.

Affected Standards: AIA MasterSpec and AWCI Standard 12 for field inspection and conformance criteria; ASTM standards for SFRM performance criteria and test methods. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard. (See Recommendation 10 for more on this issue.)

Recommendation 7. NIST recommends the adoption and use of the “structural frame” approach to fire resistance ratings.

Model Building Codes: This approach is currently required by the International Building Code (IBC), one of the model codes, and was incorporated into the 2006 edition of NFPA 5000,Building Construction and Safety Code. This requirement ensures consistency in the fire protection provided to all of the structural elements that contribute to overall structural stability. State and local jurisdictions should adopt and enforce this requirement.

Recommendation 8. NIST recommends that the fire resistance of structures be enhanced by requiring a performance objective that uncontrolled building fires result in burnout without partial or global (total) collapse.

Model Building Codes:This recommendation should be included into the national model codes as an objective and adopted as an integral part of fire resistance design for structures. The issue of non-operational sprinklers could be addressed using the existing concept of Design Scenario 8 of NFPA 5000, where such compromise is assumed and the result is required to be acceptable to the Authority Having Jurisdiction. Affected Standards: ASCE-7, AISC Specifications, ACI 318, and ASCE/SFPE 29.

Recommendation 9. NIST recommends the development of: (1) performance-based standards and code provisions, as an alternative to current prescriptive design methods, to enable the design and retrofit of structures to resist real building fire conditions, including their ability to achieve the performance objective of burnout without structural or local floor collapse: and (2) the tools, guidelines, and test methods necessary to evaluate the fire performance of the structure as a whole system.

Affected National and International Standards: ASCE-7, AISC Specifications, ACI 318, and ASCE/SFPE 29 for fire resistance design and retrofit of structures; NFPA, SFPE, ASCE, and ISO TC92 SC4 for building-specific multi-compartment, multi-floor design basis fire scenarios; and ASTM, NFPA, UL, and ISO for new test methods. Model Building Codes: The performance standards should be adopted as an alternate method in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 10. NIST recommends the development and evaluation of new fire-resistive coating materials, systems, and technologies with significantly enhanced performance and durability to provide protection following major events.

Affected Standards: Technical barriers, if any, to the introduction of new structural fire resistance materials, systems, and technologies should be identified and eliminated in the AIA MasterSpec, AWCI Standard 12 and ASTM standards for field inspection, conformance criteria, and test methods. Model Building Codes: Technical barriers, if any, to the introduction of new structural fire resistance materials, systems, and technologies should be eliminated from the model building codes.

Recommendation 11. NIST recommends that the performance and suitability of advanced structural steel, reinforced and pre-stressed concrete, and other high-performance material systems be evaluated for use under conditions expected in building fires.

Affected Standards: AISC Specifications and ACI 318. Technical barriers, if any, to the introduction of these advanced systems should be eliminated in ASTM E 119, NFPA 251, UL 263, ISO 834. Model Building Codes: Technical barriers, if any, to the introduction of these advanced systems should be eliminated from the model building codes.

Recommendation 12. NIST recommends that the performance and possibly the redundancy of active fire protection systems (sprinklers, standpipes/hoses, fire alarms, and smoke management systems) in buildings be enhanced to accommodate the greater risks associated with increasing building height and population, increased use of open spaces, high-risk building activities, fire department response limits, transient fuel loads, and higher threat profile.

Recommendation 13. NIST recommends that fire alarm and communications systems in buildings be developed to provide continuous, reliable, and accurate information on the status of life safety conditions at a level of detail sufficient to manage the evacuation process in building fire emergencies; all communication and control paths in buildings need to be designed and installed to have the same resistance to failure and increased survivability above that specified in present standards.

Affected Standards: NFPA 1, NFPA 72, and NFPA 101. Model Building and Fire Codes: The performance standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 14. NIST recommends that control panels at fire/emergency command stations in buildings be adapted to accept and interpret a larger quantity of more reliable information from the active fire protection systems that provide tactical decision aids to fireground commanders, including water flow rates from pressure and flow measurement devices, and that standards for their performance be developed.

Affected Standards: NFPA 1, NFPA 72, and NFPA 101. Model Building and Fire Codes: The performance standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 15.NIST recommends that systems be developed and implemented for: (1) real-time off-site secure transmission of valuable information from fire alarm and other monitored building systems for use by emergency responders, at any location, to enhance situational awareness and response decisions and maintain safe and efficient operations; and (2) preservation of that information either off-site or in a black box that will survive a fire or other building failure for purposes of subsequent investigations and analysis. Standards for the performance of such systems should be developed, and their use should be required.

Affected Standards: NFPA 1, NFPA 72, and NFPA 101. Model Building and Fire Codes: The performance standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 16. NIST recommends that public agencies, non-profit organizations concerned with building and fire safety, and building owners and managers develop and carry out public education and training campaigns, jointly and on a nationwide scale, to improve building occupants’ preparedness for evacuation in case of building emergencies.

Affected Standard: ICC/ANSI A117-1. Model Building and Fire Codes: The standard should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard. Affected Organizations: NFPA, NIBS, NCSBCS, BOMA, and CTBUH.

Recommendation 17.NIST recommends that tall buildings be designed to accommodate timely full building evacuation of occupants when required in building-specific or large-scale emergencies such as widespread power outages, major earthquakes, tornadoes, hurricanes without sufficient advanced warning, fires, explosions, and terrorist attack. Building size, population, function, and iconic status should be taken into account in designing the egress system. Stairwell capacity and stair discharge door width38 should be adequate to accommodate counterflow due to emergency access by responders.

Affected Standards: NFPA 101, ASME A 17. Model Building and Fire Codes: The standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 18. NIST recommends that egress systems be designed: (1) to maximize remoteness of egress components (i.e., stairs, elevators, exits) without negatively impacting the average travel distance; (2) to maintain their functional integrity and survivability under foreseeable building-specific or large-scale emergencies; and (3) with consistent layouts, standard signage, and guidance so that systems become intuitive and obvious to building occupants during evacuations.

Affected Standard: NFPA 101. Model Building and Fire Codes: The standard should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 19. NIST recommends that building owners, managers, and emergency responders develop a joint plan and take steps to ensure that accurate emergency information is communicated in a timely manner to enhance the situational awareness of building occupants and emergency responders affected by an event. This should be accomplished through better coordination of information among different emergency responder groups, efficient sharing of that information among building occupants and emergency responders, more robust design of emergency public address systems, improved emergency responder communication systems, and use of the Emergency Broadcast System (now known as the Integrated Public Alert and Warning System) and Community Emergency Alert Networks.

Affected Standard: NFPA 101 and/or a new standard. Model Building and Fire Codes: The standard should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard to the extent it is within the scope of building and fire codes.

Recommendation 20. NIST recommends that the full range of current and next generation evacuation technologies should be evaluated for future use, including protected/hardened elevators, exterior escape devices, and stairwell descent devices, which may allow all occupants an equal opportunity for evacuation and facilitate emergency response access.

Affected Standards: NFPA 101, ASME A 17, ASTM E 06, ANSI A117.1. Model Building and Fire Codes: The standards should be adopted in model building and fire codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 22. NIST recommends the installation, inspection, and testing of emergency communications systems, radio communications, and associated operating protocols to ensure that the systems and protocols: (1) are effective for large-scale emergencies in buildings with challenging radio frequency propagation environments; and (2) can be used to identify, locate, and track emergency responders within indoor building environments and in the field.

Affected Standards: FCC, SAFECOM, NFPA Standards on Electronic Safety Equipment, NFPA 70, NFPA 297, and NFPA 1221. Model Building Codes: The standards should be adopted in model building codes by mandatory reference to, or incorporation of, the latest edition of the standard.

Recommendation 23. NIST recommends the establishment and implementation of detailed procedures and methods for gathering, processing, and delivering critical information through integration of relevant voice, video, graphical, and written data to enhance the situational awareness of all emergency responders. An information intelligence sector should be established to coordinate the effort for each incident.

Recommendation 24. NIST recommends the establishment and implementation of codes and protocols for ensuring effective and uninterrupted operation of the command and control system for large-scale building emergencies.

Recommendation 25. Nongovernmental and quasi-governmental entities that own or lease buildings and are not subject to building and fire safety code requirements of any governmental jurisdiction are nevertheless concerned about the safety of the building occupants and the responding emergency personnel. NIST recommends that such entities be encouraged to provide a level of safety that equals or exceeds the level of safety that would be provided by strict compliance with the code requirements of an appropriate governmental jurisdiction. To gain broad public confidence in the safety of such buildings, NIST further recommends that asdesigned and as-built safety be certified by a qualified third party, independent of the building owner(s). The process should not use self-approval for code enforcement in areas including interpretation of code provisions, design approval, product acceptance, certification of the final construction, and post-occupancy inspections over the life of the buildings.

Recommendation 26. NIST recommends that state and local jurisdictions adopt and aggressively enforce available provisions in building codes to ensure that egress and sprinkler requirements are met by existing buildings. Further, occupancy requirements should be modified where needed (such as when there are assembly use spaces within an office building) to meet the requirements in model building codes.

Codes: Provisions related to egress and sprinkler requirements in existing buildings are available in such codes as the International Existing Building Code (IEBC), International Fire Code, NFPA 1, NFPA 101, and ASME A 17.3.

Recommendation 27. NIST recommends that building codes incorporate a provision that requires building owners to retain documents, including supporting calculations and test data, related to building design, construction, maintenance and modifications over the entire life of the building. Means should be developed for offsite storage and maintenance of the documents. In addition, NIST recommends that relevant building information be made available in suitably designed hard copy or electronic format for use by emergency responders. Such information should be easily accessible by responders during emergencies.

Model Building Codes: Model building codes should incorporate this recommendation. State and local jurisdictions should adopt and enforce these requirements.

Recommendation 28. NIST recommends that the role of the “Design Professional in Responsible Charge” be clarified to ensure that: (1) all appropriate design professionals (including, e.g., the fire protection engineer) are part of the design team providing the standard of care when designing buildings employing innovative or unusual fire safety systems, and (2) all appropriate design professionals (including, e.g., the structural engineer and the fire protection engineer) are part of the design team providing the standard of care when designing the structure to resist fires, in buildings that employ innovative or unusual structural and fire safety systems.

Affected Standards: AIA Practice Guidelines. Model Building Codes: The IBC, which already defines the “Design Professional in Responsible Charge,” be clarified to address this recommendation. The NFPA 5000 should incorporate the “Design Professional in Responsible Charge” concept and address this recommendation.

Recommendation 29. NIST recommends that continuing education curricula be developed and programs be implemented for (1) training fire protection engineers and architects in structural engineering principles and design, and (2) training structural engineers, architects, fire protection engineers, and code enforcement officials in modern fire protection principles and technologies, including fire-resistance design of structures, and (3) training building regulatory and fire service personnel to upgrade their understanding and skills to conduct the review, inspection, and approval tasks for which they are responsible.

Affected Organizations: AIA, SFPE, ASCE, ASME, AISC, ACI, and state licensing boards. Model Building Codes: Detailed criteria and requirements should be incorporated into the model building codes under the topic “Design Professional in Responsible Charge.”

Recommendation 30.NIST recommends that academic, professional short-course, and webbased training materials in the use of computational fire dynamics and thermostructural analysis tools be developed and delivered to strengthen the base of available technical capabilities and human resources.

National Fire Protection Association, NFPA 1710 – Standard for the Organization and Deployment of Fire Suppression Operations, Emergency Medical Operations, and Special Operations to the Public by Career Fire Departments